Organic light emitting diode

ABSTRACT

According to an embodiment of the present disclosure, an organic light emitting diode includes: a first electrode; a second electrode overlapping the first electrode; an emission layer positioned between the first electrode and the second electrode; an electron injection layer positioned between the emission layer and the second electrode; and an electron injection delay layer positioned between the emission layer and the electron injection layer, wherein the electron injection layer includes a first material made of a metal and a second material made of a metal halide, and the electron injection delay layer has a thickness of about 20 Å to about 140 Å.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/352,513, filed on Nov. 15, 2016, which claims priority to and thebenefit of Korean Patent Application No. 10-2016-0057493, filed in theKorean Intellectual Property Office on May 11, 2016, the entire contentsof both of which are incorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to an organic light emitting diode.

2. Description of the Related Art

An organic light emitting diode is an element (e.g., a device) in whichholes supplied from an anode and electrons supplied from a cathode arecombined in an organic emission layer to form excitons, and light isemitted when the excitons drop from an excited state to a ground state(e.g., become stabilized).

The organic light emitting diode has several merits such as wide viewingangles, fast response speed, thin thickness, and lower power consumptionsuch that the organic light emitting diode is widely applied to variouselectrical and electronic devices such as televisions, monitors, mobilephones, etc.

However, since the organic light emitting diode has low emissionefficiency, a high driving voltage is required to obtain high luminancerequired of the display or a light (e.g., an emitted light), andresultantly, a lifespan of the element (e.g., the organic light emittingdiode) may be shortened.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

An aspect according to one or more embodiments of the present disclosureis directed toward an organic light emitting diode with improvedemission efficiency.

According to an embodiment of the present disclosure, an organic lightemitting diode includes: a first electrode; a second electrodeoverlapping the first electrode; an emission layer between the firstelectrode and the second electrode; an electron injection layer betweenthe emission layer and the second electrode; and an electron injectiondelay layer between the emission layer and the electron injection layer,wherein the electron injection layer includes a reaction product of afirst material including a metal and a second material including a metalhalide, and the electron injection delay layer has a thickness fromequal to or greater than 20 Å to equal to or less than 140 Å.

The electron injection delay layer may include a dielectric materialhaving a band gap of 4 eV or more.

The electron injection delay layer may include at least one selectedfrom the group consisting of LiF, NaF, KF, RbF, CsF, MgF₂, CaF₂, SrF₂,BaF₂, Liq, and Alq₃.

A valence electron number of the metal included in the first materialmay be equal to or greater than a valence electron number of the metalincluded in the second material.

The electron injection layer may include a first compound including themetal of the first material and the halide of the second material and asecond compound including the metal of the first material and the metalhalide of the second material.

The metal of the first material included in the first compound may be abivalent element or a trivalent element.

The second compound may have a perovskite structure.

The first material may be a lanthanide metal.

The second material may be a metal iodide.

The metal iodide may include one selected from the group consisting ofLil, NaI, KI, RbI, CsI, MgI₂, CaI₂, SrI₂, and BaI₂.

In the electron injection layer, the first material may be distributedwith a same volume as the second material or the first material may bedistributed with a greater volume than the second material.

The electron injection layer may include a lower region where more firstmaterial is distributed than the second material and an upper regionwhere more second material is distributed than the first material.

The amount of the first material may increase in a direction from thesecond electrode toward the electron injection delay layer in theelectron injection layer.

The emission layer may emit white light by combining a plurality oflayers.

The plurality of layers may include two light emission layers or threelight emission layers.

The organic light emitting diode may further include an electrontransport layer between the emission layer and the electron injectiondelay layer, and the electron transport layer may include an organicmaterial.

An organic light emitting diode according to an exemplary embodiment ofthe present disclosure includes: a first electrode; a second electrodeoverlapping the first electrode; an emission layer between the firstelectrode and the second electrode; an electron injection layer betweenthe emission layer and the second electrode; and an electron injectiondelay layer between the emission layer and the electron injection layerand configured to lower an electron injection speed, wherein theelectron injection layer includes a reaction product of a first materialincluding a metal and a second material including a metal halide, and avalence electron number of the metal included in the first material isequal to or greater than a valence electron number of the metal includedin the second material.

The electron injection layer may include a first compound including themetal of the first material and the halide of the second material and asecond compound including the metal of the first material and the metalhalide of the second material.

The metal of the first material included in the first compound may be abivalent element or a trivalent element.

The second compound may have a perovskite structure.

The first material may be a lanthanide metal.

The second material may be a metal iodide.

The metal iodide may include one selected from the group consisting ofLil, NaI, KI, RbI, CsI, MgI₂, CaI₂, SrI₂, and BaI₂.

The organic light emitting diode may further include an electrontransport layer between the emission layer and the electron injectiondelay layer, and the electron transport layer may include an organicmaterial.

According to an exemplary embodiment of the present disclosure, thecharge balance is good such that the emission efficiency of the organiclight emitting diode may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an organic light emittingdiode according to an exemplary embodiment of the present disclosure.

FIG. 2 is a schematic illustration showing a perovskite structureaccording to an exemplary embodiment of the present disclosure.

FIG. 3 is a schematic cross-sectional view showing an exemplaryvariation of an electron injection layer structure in the exemplaryembodiment of FIG. 1.

FIG. 4 is a schematic illustration showing an electron injection layerhaving free electrons according to an exemplary embodiment of thepresent disclosure.

FIG. 5 is a schematic cross-sectional view showing an exemplaryembodiment incorporating an emission layer of the exemplary embodimentof FIG. 1.

FIG. 6 is a schematic cross-sectional view showing an exemplaryvariation of an emission layer according to the exemplary embodiment ofFIG. 5.

FIG. 7 is a schematic cross-sectional view showing an organic lightemitting device according to an exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Features and enhancements of the present invention will be described inmore detail hereinafter with reference to the accompanying drawings, inwhich exemplary embodiments of the present invention are shown. As thoseskilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the present invention.

In order to clearly explain the present invention, a portion that is notdirectly related to the present invention may not be provided, and thesame reference numerals refer to the same or similar constituentelements through the entire specification.

Further, in the drawings, the sizes and thicknesses of the componentsare exemplarily provided for convenience of description, and the presentinvention is not limited to those shown in the drawings. In thedrawings, the thickness of layers, films, panels, regions, etc., may beexaggerated for clarity. In the drawings, the thickness of layers,films, panels, regions, etc., may be exaggerated for convenience ofdescription.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present. Further,in the specification, the word “on” or “above” refers to positions on orbelow the object portion, and does not necessarily refer to a positionon the upper side of the object portion based on a gravitationaldirection.

In addition, unless explicitly described to the contrary, the word“comprise” and variations thereof (such as “comprises” or “comprising”)will be understood to imply the inclusion of the stated elements but notthe exclusion of any other elements.

Further, in this specification, the phrase “on a plane” refers toviewing a target portion from the top, and the phrase “on across-section” refers to viewing a cross-section formed by verticallycutting a target portion from the side.

Expressions such as “at least one of” or “at least one selected from”when preceding a list of elements, modify the entire list of elementsand do not modify the individual elements of the list. Further, the useof “may” when describing embodiments of the present invention refers to“one or more embodiments of the present invention.” Also, the term“exemplary” is intended to refer to an example or illustration.

As used herein, the terms “substantially,” “about,” and similar termsare used as terms of approximation and not as terms of degree, and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. Also, any numerical range recited herein is intended to includeall sub-ranges of the same numerical precision subsumed within therecited range. For example, a range of “1.0 to 10.0” is intended toinclude all subranges between (and including) the recited minimum valueof 1.0 and the recited maximum value of 10.0, that is, having a minimumvalue equal to or greater than 1.0 and a maximum value equal to or lessthan 10.0, such as, for example, 2.4 to 7.6. Any maximum numericallimitation recited herein is intended to include all lower numericallimitations subsumed therein and any minimum numerical limitationrecited in this specification is intended to include all highernumerical limitations subsumed therein. Accordingly, Applicant reservesthe right to amend this specification, including the claims, toexpressly recite any sub-range subsumed within the ranges expresslyrecited herein.

FIG. 1 is a schematic cross-sectional view of an organic light emittingdiode according to an exemplary embodiment of the present disclosure.FIG. 2 is a schematic illustration showing a perovskite structureaccording to an exemplary embodiment of the present disclosure.

Referring to FIG. 1, an organic light emitting diode according to thepresent exemplary embodiment includes a first electrode 120 and a secondelectrode 190 overlapping each other, an emission layer 150 positionedbetween the first electrode 120 and the second electrode 190, a holetransport region 130 positioned between the first electrode 120 and theemission layer 150, an electron transport layer 160 positioned betweenthe emission layer 150 and the second electrode 190, an electroninjection layer 180 positioned between the electron transport layer 160and the second electrode 190, an electron injection delay layer 170positioned between the electron transport layer 160 and the electroninjection layer 180, and a capping layer 200 positioned on the secondelectrode 190.

In the present exemplary embodiment, the first electrode 120 may be areflecting electrode.

In the present disclosure, the reflecting electrode may be defined as anelectrode including a material having a characteristic of reflectinglight emitted from the emission layer 150 to be transmitted to thesecond electrode 190. The reflection characteristic may refer to areflectivity of incident light that is about 70% or more to about 100%or less, or about 80% or more to about 100% or less.

The first electrode 120 may include silver (Ag), aluminum (Al), chromium(Cr), molybdenum (Mo), tungsten (W), titanium (Ti), gold (Au), palladium(Pd), or alloys thereof to be utilized as the reflection layer whilehaving the anode function, and may have a triple layer structure ofsilver (Ag)/indium tin oxide (ITO)/silver (Ag) or indium tin oxide(ITO)/silver (Ag)/indium tin oxide (ITO).

The first electrode 120 may be formed by utilizing a sputtering method,a vapor phase deposition method, an ion beam deposition method, or anelectron beam deposition method.

The hole transport region 130 may correspond to an auxiliary layerpositioned between the first electrode 120 and the emission layer 150.The hole transport region 130 may include at least one of the holeinjection layer and the hole transport layer. The hole injection layerfacilitates injection of holes from the first electrode 120, and thehole transport layer performs a function of smoothly transporting theholes transmitted from the hole injection layer. The hole transportregion 130 may be formed of a dual-layered structure in which the holetransport layer is disposed on the hole injection layer, or a singlelayer in which a material forming the hole injection layer and thematerial forming the hole transport layer are mixed.

The hole transport region 130 may include an organic material. Forexample, the hole transport region 130 may include NPD(N,N-dinaphthyl-N,N′-diphenyl benzidine), TPD (N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine), spiro-TAD, and/orMTDATA (4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine),but embodiments of the present disclosure are not limited thereto.

The emission layer 150 is positioned on the hole transport region 130.The emission layer 150 includes a light emitting material displaying aparticular color. For example, the emission layer 150 may display aprimary color such as blue, green, or red, or a combination thereof.

The thickness of the emission layer 150 may be in a range from 10 nm to50 nm. The emission layer 150 may include a host and a dopant. Theemission layer 150 may contain materials for emitting red, green, blue,and/or white light, and may be formed by utilizing a phosphorescentand/or fluorescent material.

When the emission layer 150 emits red light, the emission layer 150 mayinclude a host material that includes CBP(4,4′-bis(carbazol-9-yl)-biphenyl) or mCP (1,3-bis(carbazol-9-yl)benzene), and may further include a phosphorescent material including atleast one selected from PIQIr(acac)(bis(1-phenylisoquinoline)acetylacetonate iridium), PQIr(acac)(bis(1-phenylquinoline)acetylacetonate iridium), PQIr(tris(1-phenylquinoline)iridium), and PtOEP (platinumoctaethylporphyrin), or a fluorescent material includingPBD:Eu(DBM)3(phen) or perylene, but embodiments of the presentdisclosure are not limited thereto.

When the emission layer 150 emits green light, the emission layer 150may include a host material including CBP or mCP, and may furtherinclude a phosphorescent material including a dopant material includingIr(ppy)3 (fac-tris(2-phenylpyridine)iridium) or a fluorescent materialincluding Alq3(tris(8-hydroxyquinolino)aluminum), but embodiments of thepresent disclosure are not limited thereto.

When the emission layer 150 emits blue light, the emission layer 150 mayinclude a host material including CBP or mCP, and may further include aphosphorescent material including a dopant that includes(4,6-F2ppy)2Irpic. Alternatively, the emission layer 150 may include thehost material having an anthracene group, and may further include afluorescent material including the dopant including a diamine group orat least one selected from spiro-DPVBi, spiro-6P, distyrylbenzene (DSB),distyrylarylene (DSA), a PFO-based polymer, and a PPV-based polymer, butembodiments of the present disclosure are not limited thereto.

The electron transport layer 160 and the electron injection layer 180are positioned between the emission layer 150 and the second electrode190. The electron transport layer 160 is positioned to be adjacent tothe emission layer 150, and the electron injection layer 180 ispositioned to be adjacent to the second electrode 190.

The electron transport layer 160 may include an organic material. Forexample, the electron transport layer 160 may be made of at least oneselected from Alq₃ (tris(8-hydroxyquinolino)aluminum), PBD(2-[4-biphenyl-5-[4-tert-butylphenyl]]-1,3,4-oxadiazole), TAZ(1,2,4-triazole),spiro-PBD(spiro-2-[4-biphenyl-5-[4-tert-butylphenyl]]-1,3,4-oxadiazole),BAlq (8-hydroxyquinoline aluminum salt; for example, 8-hydroxyquinolinealuminum salt may bebis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)-aluminum),and 8-hydroxyquinoline beryllium salt, however embodiments of thepresent disclosure are not limited thereto.

The electron transport layer 160 may transmit the electrons from thesecond electrode 190 to the emission layer 150. Also, the electrontransport layer 160 may reduce or prevent the holes injected from thefirst electrode 120 from being moved into the second electrode 190through the emission layer 150. That is, the electron transport layer160 has a function of a hole blocking layer and helps with thecombination of the holes and the electrons in the emission layer 150.

The electron injection layer 180 has a function of improving theelectron injection from the second electrode 190 to the electrontransport layer 160. In the present exemplary embodiment, the electroninjection layer 180 may include a reaction product of a first materialmade of (e.g., including or consisting of) a metal and a second materialmade of (e.g., including or consisting of) a metal halide. The firstmaterial may be a lanthanide metal, and the second material may behalides of Group 1 elements or Group 2 elements, for example, the secondmaterial may be a metal iodide.

In the present exemplary embodiment, the thickness of the electroninjection layer 180 may be in a range from about 2 Å to about 25 Å byconsidering a process margin.

In the present exemplary embodiment, the first material and the secondmaterial may include metals having standard electrode potentials thatare similar to each other. For example, when the first material and thesecond material include any one among Group 1 elements, Group 2elements, and lanthanide elements, generation of a spontaneous reactiondue to strong reactivity has been experimentally confirmed.

Experimental Example

Through this experiment, the first material made of the lanthanideelements such as ytterbium (Yb), europium (Eu), thulium (Tm), and/orsamarium (Sm) and the second material made of the metal iodide such asRbI (rubidium iodide) and/or CsI (cesium iodide) are combined andco-deposited, and the first material and the second material are reacted(e.g., spontaneously reacted while being co-deposited), thereby formingthe layer (e.g., the electron injection layer).

In this case, a result that the conductivity rises (increases) while thelayer becomes transparent occurs. However, instead of the above, if thefirst material made of silver (Ag) and the second material made of themetal iodide such as RbI and/or CsI are combined and co-deposited toform the layer (e.g., the electron injection layer), the layer is nottransparent and the conductivity does not rise (increase). Also, whencombining and co-depositing the first material made of the lanthanideelements such as Yb, Eu, Tm, and/or Sm and the second material made ofCuI to be reacted to form the layer (e.g., the electron injectionlayer), the layer is not transparent and the conductivity does not rise(increase). Accordingly, according to embodiments of the presentdisclosure, the metals included in the first material and the secondmaterial are materials having high reactivity to induce the spontaneousreaction.

Among the halide compounds, an iodine compound has low electron affinityof iodine itself and low electronegativity, thus it is easy for theiodine compound to be dissociated to form an iodine vacancy or becombined with other reactive metals to generate a new compound.Accordingly, the electron injection characteristic may be improved bythe compounds generated by a substitution reaction of the first materialmade of the metal and the second material made of the metal iodideincluding iodine.

Also, since iodine has a small refractive index difference with theorganic material compared to fluorine, it is enhanced (e.g,advantageous) for optical design. Further, since iodine has a lowthermal evaporation temperature compared to the material such asfluorine, a process characteristic is enhanced (e.g, advantageous). Inaddition, if fluorine is pyrolyzed, a gas is emitted such that a vacuumdegree (in the processing chamber) is decreased, however, even thoughheat is applied to iodine, it remains solid and there is no problem ofthe decreasing vacuum degree.

A conduction mechanism will be described below.

In the present exemplary embodiment, the metal included in the firstmaterial and the metal included in the second material may besubstituted with each other. In this case, a valence electron number ofthe first material may be equal to or greater than a valence electronnumber of the metal included in the second material. If the valenceelectron number of the metal included in the first material is greaterthan the valence electron number of the metal included in the secondmaterial, the conductivity due to the free electrons that areadditionally generated may be improved.

Also, if the halogen elements included in the second material are movedinto (e.g., combined with) the first material to form a new material,free electrons are formed due to a halogen vacancy, such thatconductivity may be improved.

Also, conductivity may be improved by the remaining metal ions thatparticipate in the reaction (between the first material and the secondmaterial).

In the present exemplary embodiment, the electron injection layer 180(e.g., the reaction product forming the electron injection layer 180)may include a first compound made of (e.g., including or consisting of)the metal of the first material and the halide of the second materialand a second compound made of (e.g., including or consisting of) themetal of the first material and the metal halide of the second material.In this case, in the first compound, the metal of the first material maybe a bivalent element or a trivalent element. The second compound mayhave a perovskite structure.

For example, the first material may be Yb, and the second material maybe RbI. If RbI and Yb are co-deposited or the deposition is performed byutilizing each material, the chemical reaction is generated, therebygenerating at least one among YbI₂, YbI₃, and RbYbI₃. Here, RbYbI₃, asshown in FIG. 2, may have the perovskite structure. In this way,although the chemical reaction is generated, the remaining material alsoexists as RbI.

The electron injection layer 180 according to the present exemplaryembodiment may be a single-layered structure in which the first materialand the second material are co-deposited. In the electron injectionlayer 180, if the first material is more greatly distributed (e.g., hasa greater volume fraction) than the second material, the conductivitymay be relatively increased or the transmittance may be relativelyreduced compared with the opposite case (e.g., where the second materialhas a greater volume fraction than the first material). However,embodiments of the present disclosure are not limited thereto, thesecond material may be more greatly distributed compared with the firstmaterial in the electron injection layer 180. Accordingly, in thepresent exemplary embodiment, a degree (volume) at which the firstmaterial and the second material are distributed may be enhanced (e.g.,optimized) by considering the sheet resistance and transmittancerequired of the organic light emitting diode. Also, the first materialand the second material included in the electron injection layer 180 maybe substantially distributed with the same volume.

In the present exemplary embodiment, the electron injection delay layer170 is positioned between the electron transport layer 160 and theelectron injection layer 180. The electron injection delay layer 170 hasa function of reducing or preventing the electron injection layer 180according to the present exemplary embodiment from very quickly movingthe electrons transmitted from the second electrode 190 into theemission layer 150.

The electron injection delay layer 170 includes a dielectric materialhaving a band gap of 4 eV or more. In this case, the electron injectiondelay layer 170 may include at least one selected from LiF, NaF, KF,RbF, CsF, MgF₂, CaF₂, SrF₂, BaF₂, Liq, and Alq₃. However, if heat isapplied, the process characteristic is decreased for LiF, or theoxidation is easily generated and the vacuum (in the processing chamber)is decreased for CaF₂. Therefore, according to an embodiment of thepresent disclosure, the materials (such as NaF, KF, RbF, CsF, MgF₂,SrF₂, BaF₂, Liq, and Alq₃) except for LiF and CaF₂ are utilized in theelectron injection delay layer 170.

TABLE 1 Red Blue Driving Emission Driving Emission voltage efficiencyvoltage Efficiency Comparative 5.5 50 4.2 123 Example 1 Comparative 5.918 4.8 115 Example 2 Comparative 5.5 52 4.3 128 Example 3 Reference 5.425.3 4.1 130 Example 1 Exemplary 4.6 55.2 3.8 142 Embodiment 1 Exemplary4.5 57.4 3.7 148 Embodiment 2 Exemplary 4.2 61.3 3.5 152 Embodiment 3Exemplary 4.3 60.2 3.8 149 Embodiment 4 Exemplary 4.5 57.2 3.9 148Embodiment 5 Exemplary 4.7 55.1 4.0 145 Embodiment 6 Reference 5.3 23.24.5 110 Example 2

In Table 1, the organic light emitting diode is manufactured to have thecathode including AgMg to measure the driving voltage and the emissionefficiency in red and blue elements.

In Table 1, Comparative Example 1 has the electron injection layerincluding Yb at about 13 Å, Comparative Example 2 has the electroninjection layer at the thickness of about 13 Å obtained by co-depositingRbI and Yb, and Comparative Example 3 has the electron injection layerincluding LiF at about 10 Å. Reference example 1, Reference example 2,and Exemplary Embodiment 1 to Exemplary Embodiment 6 each have theelectron injection layer at the thickness of about 13 Å obtained byco-depositing RbI and Yb and the electron injection delay layer 170positioned to be adjacent to the electron transport layer 160. In thiscase, the electron injection delay layer 170 utilizes Liq.

In Reference Example 1 and Reference Example 2, the thickness of theelectron injection delay layer 170 is 10 Å and 150 Å, respectively, andcompared with Comparative Example 1, Comparative Example 2, andComparative Example 3, the driving voltage is slightly reduced and theemission efficiency is rather poor.

In Exemplary Embodiment 1 to Exemplary Embodiment 6, the thickness ofthe electron injection delay layer 170 is 30 Å, 50 Å, 70 Å, 90 Å, 110 Å,and 130 Å, respectively.

In Exemplary Embodiment 1 to Exemplary Embodiment 6 in which thethickness of the electron injection delay layer 170 has the range ofabout 20 Å to about 140 Å (considering the processing margin), comparedwith Comparative Example 1 to Comparative Example 3, it may be confirmedthat the driving voltage is reduced and the emission efficiency isimproved. According to an embodiment of the present disclosure, thethickness of the electron injection delay layer 170 may be in the rangefrom about 30 Å to about 130 Å.

The second electrode 190 is positioned on the electron injection layer180. The second electrode 190 may be a transflective electrode.

In the present disclosure, the transflective electrode may be defined asan electrode including a material having a transflective characteristictransmitting part of the light incident to the second electrode 190 andreflecting a remaining part of the light to the first electrode 120.Here, the transflective characteristic may refer to that thereflectivity for the incident light is about 0.1% or more to about 70%or less, or about 30% or more to about 50% or less.

The second electrode 190 may include silver (Ag), magnesium (Mg),aluminum (Al), chromium (Cr), molybdenum (Mo), tungsten (W), titanium(Ti), gold (Au), palladium (Pd), ytterbium (Yb), or one or more alloysthereof.

When the above-described second electrode 190 is formed of the alloy, analloy ratio is controlled by a temperature of a deposition source, anatmosphere, and a vacuum degree, and may be selected as an appropriateratio. In the present exemplary embodiment, the second electrode 190 mayhave a thickness from about 50 Å (angstroms) to about 150 Å. If thethickness of the second electrode 190 is smaller than 50 Å, it isdifficult to obtain the sheet resistance, while if the thickness isgreater than 150 Å, the reflectance is increased without a wide angledistribution (WAD) such that a color change may be generated when beingviewed from the side.

In the present exemplary embodiment, the second electrode 190 may beformed of AgMg, a content of Ag included in the second electrode 190 maybe over 50 atomic % (at %), and Ag may be more abundant than Mg.

The capping layer 200 is positioned on the second electrode 190, and maybe formed of an organic material or an inorganic material and may have afunction of protecting the second electrode 190 or guiding a change ofresonance intensity and resonance phase along with the second electrode190.

As described above, the organic light emitting diode according to thepresent exemplary embodiment has the electron injection layer 180including the reaction product of the first material made of the metaland the second material made of the metal halide. The metal halide maybe the metal iodide.

Here, if a voltage is applied to the first electrode 120 and the secondelectrode 190, the metal iodide of an ion combination state is alignedinto positive charges/negative charges depending on the electric fieldinside a dipole thin film (the electron injection layer in the presentexemplary embodiment) by the electric field. The electrons-holessymmetrized in the interface of the electron transport layer 160 and thesecond electrode 190 based on the dipole thin film are coupled with adipole surface, and excess electrons and holes by the amount offset forthe voltage maintaining exist in the interface. In this case, like RbIincluded in the electron injection layer 180 according to the presentexemplary embodiment, in a case of a polarized molecule having a dipolemoment without the electric field, as the value of the dipole moment isgreater, the coupled amount in the interface is increased and the amountof the electrons and the holes existing in the interface is greater.Particularly, the interface of the electron transport layer 160including the organic material in which the holes are gathered to becharged with the positive charges is realized as a base (space) wherethe electrons are absent, and this may lead to many electrons movinginto the vacancies. In this case, a vacuum level of the interface of theelectron transport layer 160 is shifted (lowering a LUMO level) suchthat the injection barrier is lowered. Additionally, the introducedmetal having the work function of less than 4.0 eV such as Yb has thefunction to make the interface charged with the positive charges due toa characteristic of an electron donor such that the electron injectioncharacteristic may be further improved.

However, a charge balance is lower due to the excessively improvedelectron injection performance such that there is a problem that theemission efficiency relatively falls (is lowered), and in the presentexemplary embodiment, the electron injection delay layer 170 isintroduced to align (e.g., control the electron injection and maintain)the charge balance.

FIG. 3 is a schematic cross-sectional view showing an exemplaryvariation of an electron injection layer structure in the exemplaryembodiment of FIG. 1.

Referring to FIG. 3, most configurations are the same as those of theexemplary embodiment of FIG. 1, and like the exemplary embodiment ofFIG. 1, the electron injection layer 180 includes a reaction product ofthe first material made of the metal and the second material made of themetal halide. However, in the present exemplary embodiment, the electroninjection layer 180 also includes a lower region 180 a and an upperregion 180 b, the first material is more greatly distributed than thesecond material in the lower region 180 a (e.g., more first materialthan the second material is present in the lower region 180 a), and thesecond material is more greatly distributed than the first material inthe upper region 180 b (e.g., more second material than the firstmaterial is present in the upper region 180 b). The first material issubstituted and reacted with the metal included in the second materialor a new compound is generated in the border where the lower region 180a and the upper region 180 b meet and its surrounding (areas) such thatthe conductive material may be formed. This conductive material mayinclude the free electrons and the metal ions. For example, when RbI andYb are reacted, RbI and Yb are substituted such that YbI₂ and/or YbI₃ isformed, or the material having the perovskite structure such as RbYbI₃may be formed. In this case, as Rb⁺ is substituted with Yb²⁺ or Yb³⁺,the conductivity may be improved by the generated free electrons (thefree electrons due to the iodine vacancy), and/or the metal ions (suchas Rb⁺, Yb²⁺, and Yb³⁺).

The electron injection layer 180 according to the present exemplaryembodiment may be formed as follows. A lower layer made of the firstmaterial is formed on the electron injection delay layer 170, and anupper layer made of the second material is formed on the lower layer. Inthis case, the first material of the lower layer and the second materialof the upper layer are respectively diffused without additional heattreatment, and the first material and the second material are reacted,thereby forming the layer having transparency and conductivity.

The exemplary description of the first material and the second materialdescribed in association with FIG. 1 may be applied to the presentexemplary embodiment.

FIG. 4 is a schematic illustration showing an electron injection layerhaving free electrons according to an exemplary embodiment of thepresent disclosure.

Referring to FIG. 4, one layer may be formed by utilizing Yb included inthe first material and RbI included in the second material. Yb and RbImay be reacted, thereby forming the conductor, and in more detail, Rband Yb are substituted with each other, resultantly one or two freeelectrons may be formed somewhere in the reactant, or one or two freeelectrons may be formed by the iodine vacancy generated as the YbI₂ orYbI₃ compound is formed. In this way, because of the free electronformed by RbI (that is one kind of the metal halide) and/or the freeelectron formed by the iodine vacancy, and the metal ion, the electroninjection layer 180 according to the present exemplary embodiment mayhave the conductivity of which the electron injection speed is veryfast.

FIG. 5 is a schematic cross-sectional view showing an exemplaryembodiment incorporating an emission layer of the exemplary embodimentof FIG. 1.

Referring to FIG. 5, the emission layer 150 of FIG. 1 includes a redemission layer 150R, a green emission layer 150G, and a blue emissionlayer 150B, and they are horizontally disposed in the direction parallelto the first electrode 120. Among the red emission layer 150R, the greenemission layer 150G, and the blue emission layer 150B, a pixeldefinition layer may be positioned between adjacent emission layers.

In the present exemplary embodiment, an auxiliary layer BIL to increasethe efficiency of the blue emission layer 150B may be positioned underthe blue emission layer 150B, and the auxiliary layer BIL may have afunction of increasing the efficiency of the blue emission layer 150B bycontrolling a hole charge balance. The auxiliary layer BIL may include acompound represented by Chemical Formula 1.

In Chemical Formula 1, A1, A2, and A3 are each independently an alkylgroup, an aryl group, carbazolyl, dibenzothiophenyl, dibenzofuranyl(DBF), or biphenyl, and a, b, and c are each an integer selected fromzero to four.

Examples of the compounds represented by Chemical Formula 1 include theChemical Formulas 1-1, 1-2, 1-3, 1-4, 1-5, and 1-6.

In another exemplary embodiment, the auxiliary layer (BIL) may include acompound represented by Chemical Formula 2.

In Chemical Formula 2, a, b and c may respectively be an integerselected from 0 to 3, X may be O, N, or S, and each X may be the same asor different from the other.

Examples of the compound represented by Chemical Formula 2 includeChemical Formulas 2-1, 2-2, 2-3, 2-4, and 2-5.

In another exemplary embodiment, the auxiliary layer (BIL) may include acompound represented by Chemical Formula 3.

In Chemical Formula 3, A1 may be an alkyl group, an aryl group,carbazolyl, dibenzothiophenyl, or dibenzofuranyl (DBF), L1 and L2 may be

(wherein n is an integer selected from 0 to 3), and DBF connected to L1and L2 may be each independently replaced by carbazolyl ordibenzothiophenyl.

In the organic light emitting diode according to the present exemplaryembodiment, a red resonance auxiliary layer 150R′ may be positionedunder the red emission layer 150R, and a green resonance auxiliary layer150G′ may be positioned under the green emission layer 150G. The redresonance auxiliary layer 150R′ and the green resonance auxiliary layer150G′ are added to control a resonance distance for each color. In oneembodiment, a separate resonance auxiliary layer positioned between theblue emission layer 150B and the auxiliary layer BIL, and between theauxiliary layer BIL and the hole transport region 130, may not be formedunder the blue emission layer 150B and the auxiliary layer BIL.

FIG. 6 is a schematic cross-sectional view showing an exemplaryvariation of an emission layer according to the exemplary embodiment ofFIG. 5.

Most of the configurations of FIG. 6 are the same as those of theorganic light emitting diode described in FIG. 1. Next, differences fromthe exemplary embodiment of FIG. 1 will be described, and the contentsdescribed with reference to FIG. 1 may all be applied to the exemplaryembodiment of FIG. 6.

Referring to FIG. 6, the organic light emitting diode according to thepresent exemplary embodiment includes the emission layer 150 emittingthe white light by combining a plurality of layers 150 a, 150 b, and 150c representing different colors. The plurality of layers may be astructure in which two light emission layers or three light emissionlayers are deposited, and the emission layer 150 of three light emissionlayers is shown in FIG. 6.

Three layers of the emission layer 150 may respectively represent blue,yellow, and blue (e.g., blue emission layer, yellow emission layer andblue emission layer), and although not shown, two layers of the emissionlayer may respectively represent blue and yellow (e.g., blue emissionlayer and yellow emission layer). Although not shown, at least onecharge generating layer may be positioned between adjacent layers amongthe plurality of layers 150 a, 150 b, and 150 c of FIG. 6.

The description related to the electron injection layer 180 and theelectron injection delay layer 170 shown in FIG. 1 may also be appliedto the organic light emitting diode of FIG. 6.

FIG. 7 is a schematic cross-sectional view showing an organic lightemitting diode display according to an exemplary embodiment of thepresent disclosure.

Referring to FIG. 7, the organic light emitting diode display accordingto an exemplary embodiment of the present disclosure includes asubstrate 23, a driving thin film transistor 30, a first electrode 120,a light-emitting element layer 100, and a second electrode 190. Thefirst electrode 120 may be the anode and the second electrode 190 may bethe cathode, however the first electrode 120 may be the cathode and thesecond electrode 190 may be the anode.

A substrate buffer layer 26 may be positioned on the substrate 23. Thesubstrate buffer layer 26 serves to reduce or prevent penetration ofimpure elements and to planarize the surface, however, the substratebuffer layer 26 is not a necessary configuration, and may not beincluded according to kind and process conditions of the substrate 23.

A driving semiconductor layer 37 is formed on the substrate buffer layer26. The driving semiconductor layer 37 may be formed of a materialincluding a polysilicon. Also, the driving semiconductor layer 37includes a channel region 35 not doped with an impurity, and a sourceregion 34 and a drain region 36 doped with an impurity (e.g., an ionmaterial) at respective sides of the channel region 35. The doped ionmaterials may be P-type impurities such as boron (B), and B₂H₆ may begenerally utilized. The impurities depend on the kind of the thin filmtransistor.

A gate insulating layer 27 is positioned on the driving semiconductorlayer 37. A gate wire including a driving gate electrode 33 ispositioned on the gate insulating layer 27. The driving gate electrode33 overlaps at least a portion of the driving semiconductor layer 37,particularly, the channel region 35.

An interlayer insulating layer 28 covering the driving gate electrode 33is formed on the gate insulating layer 27. A first contact hole 22 a anda second contact hole 22 b that expose the source region 34 and thedrain region 36 of the driving semiconductor layer 37 are formed in thegate insulating layer 27 and the interlayer insulating layer 28. A datawire including a driving source electrode 73 and a driving drainelectrode 75 may be positioned on the interlayer insulating layer 28.The driving source electrode 73 and the driving drain electrode 75 arerespectively connected to the source region 34 and the drain region 36of the driving semiconductor layer 37 through the first contact hole 22a and the second contact hole 22 b formed in the interlayer insulatinglayer 28 and the gate insulating layer 27.

As described above, the driving thin film transistor 30 (including thedriving semiconductor layer 37, the driving gate electrode 33, thedriving source electrode 73, and the driving drain electrode 75) isformed. The configuration of the driving thin film transistor 30 is notlimited to the aforementioned example, and may be variously modified tohave a suitable configuration as apparent to those skilled in the art.

In addition, a planarization layer 24 covering the data wire is formedon the interlayer insulating layer 28. The planarization layer 24 servesto remove and planarize a step in order to increase emission efficiencyof the organic light emitting diode to be formed thereon. Also, theplanarization layer 24 has a third contact hole 22 c to electricallyconnect the driving drain electrode 75 and the first electrode 120 thatis to be described later.

This exemplary embodiment of the present disclosure is not limited tothe above-described configuration, and one of the planarization layer 24and the interlayer insulating layer 28 may not be included in somecases.

A first electrode 120 of the organic light emitting diode LD ispositioned on the planarization layer 24. A pixel definition layer 25 ispositioned on the planarization layer 24 and the first electrode 120.The pixel definition layer 25 has an opening overlapping a part of thefirst electrode 120. The light-emitting element layer 100 may bepositioned in each opening formed in the pixel definition layer 25.

On the other hand, the light-emitting element layer 100 is positioned onthe first electrode 120. The light-emitting element layer 100corresponds to the hole transport region 130, the emission layer 150,the electron transport layer 160, the electron injection delay layer170, and the electron injection layer 180 in the organic light emittingdiode described in FIG. 1.

A second electrode 190 and a capping layer 200 are positioned on thelight-emitting element layer 100.

A thin film encapsulation layer 300 is positioned on the capping layer200. The thin film encapsulation layer 300 encapsulates the organiclight emitting diode LD and the driving circuit unit formed on thesubstrate 23 from the outside to protect them.

The thin film encapsulation layer 300 includes encapsulation organiclayers 300 a and 300 c and encapsulation inorganic layers 300 b and 300d that are alternately deposited one by one. In FIG. 7, the thin filmencapsulation layer 300 is configured by alternately depositing twoencapsulation organic layers 300 a and 300 c and two encapsulationinorganic layers 300 b and 300 d one by one, as an example, howeverembodiments of the present disclosure are not limited thereto.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, and equivalents thereof.

What is claimed is:
 1. An organic light emitting diode comprising: afirst electrode; a second electrode overlapping the first electrode; anemission layer between the first electrode and the second electrode; anelectron injection layer between the emission layer and the secondelectrode; an electron injection delay layer between the emission layerand the electron injection layer, wherein the electron injection delaylayer comprises at least one selected from the group consisting of LiF,NaF, KF, RbF, CsF, MgF₂, CaF₂, SrF₂, BaF₂, Liq, and Alq₃; and anelectron transport layer comprising an organic material, wherein theelectron transport layer is between the emission layer and the electroninjection delay layer, wherein the electron transport layer is incontact with the emission layer and in contact with the electroninjection delay layer, and wherein the electron injection layercomprises a metal halide.
 2. The organic light emitting diode of claim1, wherein the electron injection delay layer comprises a dielectricmaterial.
 3. The organic light emitting diode of claim 2, wherein thedielectric material has a band gap of 4 eV or more.
 4. The organic lightemitting diode of claim 1, wherein the electron injection delay layerhas a thickness from equal to or greater than 20 Å to equal to or lessthan 140 Å.
 5. The organic light emitting diode of claim 1, wherein theelectron injection layer comprises a first compound and a secondcompound, the first compound comprises an A compound and a B compound,the second compound comprises the A compound and the B compound, and theA compound comprises a metal and the B compound comprises a metalhalide.
 6. The organic light emitting diode of claim 5, wherein avalence electron number of the metal of the A compound is equal to orgreater than a valence electron number of the metal of the B compound.7. The organic light emitting diode of claim 5, wherein the metal of theA compound is a bivalent element or a trivalent element.
 8. The organiclight emitting diode of claim 5, wherein the second compound has aperovskite structure.
 9. The organic light emitting diode of claim 5,wherein the A compound is a lanthanide metal.
 10. The organic lightemitting diode of claim 5, wherein the B compound is a metal iodide. 11.The organic light emitting diode of claim 10, wherein the metal iodidecomprises one selected from the group consisting of Lil, NaI, KI, RbI,CsI, MgI₂, CaI₂, SrI₂, and BaI₂.
 12. The organic light emitting diode ofclaim 5, wherein in the electron injection layer, the A compound isdistributed with a same as the B compound or the A compound isdistributed with greater than the B compound.
 13. The organic lightemitting diode of claim 1, wherein the emission layer includes aplurality of layers.
 14. The organic light emitting diode of claim 13,wherein each layer of the plurality of layers respectively emits blue oryellow.
 15. The organic light emitting diode of claim 14, wherein theemission layer is to emit white light by combining the plurality oflayers.
 16. The organic light emitting diode of claim 15, wherein theplurality of layers comprises two light emission layers or three lightemission layers.
 17. The organic light emitting diode of claim 5,wherein the electron injection layer includes a lower region where moreof the A compound than the B compound is distributed and an upper regionwhere more of the B compound than the A compound is distributed.
 18. Theorganic light emitting diode of claim 5, wherein an amount of the Acompound increases in a direction from the second electrode toward theelectron injection delay layer in the electron injection layer.
 19. Theorganic light emitting diode of claim 1, wherein the electron injectionlayer is transparent.
 20. The organic light emitting diode of claim 5,wherein the A compound consists of the metal and the B compound consistsof the metal halide.
 21. An organic light emitting diode comprising: afirst electrode; a second electrode overlapping the first electrode; anemission layer between the first electrode and the second electrode; anelectron injection layer between the emission layer and the secondelectrode; and an electron injection delay layer between the emissionlayer and the electron injection layer, wherein the electron injectionlayer comprises an A compound and a B compound and the A compoundcomprises a metal and the B compound comprises a metal halide, and theelectron injection delay layer has a thickness from equal to or greaterthan 20 Å to equal to or less than 140 Å, and wherein the electroninjection layer includes a lower region where more of the A compoundthan the B compound is distributed and an upper region where more of theB compound than the A compound is distributed.
 22. The organic lightemitting diode of claim 21, wherein an amount of the A compoundincreases in a direction from the B compound toward the electroninjection delay layer in the electron injection layer.
 23. An organiclight emitting diode comprising: a first electrode; a second electrodeoverlapping the first electrode; an emission layer between the firstelectrode and the second electrode; an electron injection layer betweenthe emission layer and the second electrode; an electron injection delaylayer between the emission layer and the electron injection layer, andan electron transport layer comprising an organic material and betweenthe emission layer and the electron injection delay layer, wherein theelectron transport layer is in contact with the emission layer and incontact with the electron injection delay layer, wherein the electroninjection layer comprises an A compound and a B compound, and the Acompound comprises a metal and the B compound comprises a metal halide,and a valence electron number of the metal comprised in the A compoundis equal to or greater than a valence electron number of the metalcomprised in the B compound.
 24. The organic light emitting diode ofclaim 23, wherein the electron injection layer comprises a firstcompound and a second compound, the first compound comprises the Acompound and the B compound, the second compound comprises the Acompound and the B compound.
 25. The organic light emitting diode ofclaim 24, wherein the metal of the A compound in the first compound is abivalent element or a trivalent element.
 26. The organic light emittingdiode of claim 24, wherein the second compound has a perovskitestructure.
 27. The organic light emitting diode of claim 23, wherein theA compound is a lanthanide metal.
 28. The organic light emitting diodeof claim 23, wherein the B compound is a metal iodide.
 29. The organiclight emitting diode of claim 28, wherein the metal iodide comprises oneselected from the group consisting of Lil, NaI, KI, RbI, CsI, MgI₂,CaI₂, SrI₂, and BaI₂.
 30. The organic light emitting diode of claim 23,wherein the electron injection delay layer has a thickness from equal toor greater than 20 Å to equal to or less than 140 Å.
 31. The organiclight emitting diode of claim 23, wherein the electron injection delaylayer comprises at least one selected from the group consisting of LiF,NaF, KF, RbF, CsF, MgF₂, CaF₂, SrF₂, BaF₂, Liq, and Alq₃.